1. Field of the Invention
This invention relates to copolymerizable light absorber monomers and, more particularly, to .alpha.,.beta.-unsaturated dicarboxylic acid half-esters of 2-hydroxy,alkoxy,methylolbenzophenes, which can copolymerize with various unsaturated monomers to provide copolymer materials having improved resistance to degradation by light.
2. Description of the Prior Art
Various organic compounds exhibit the power to absorb electromagnetic radiation and can be incorporated in various plastic materials such as transparent sheets which act as filters for all the radiation passing through and will transmit only such radiations as are not absorbed by the sheet and/or the absorbing agent. Such filters find use in many technical and commercial applications.
Numerous acrylic compounds have been suggested as absorbents for the range of radiations described above. For specific compounds, see U.S. Pat. Nos. 3,081,280; 3,272,810; 3,644,466; 3,256,312 and 3,215,724. These ultraviolet absorbers are mechanically mixed with the plastic materials to prevent discoloration and degradation of the material. However, it has been observed that such absorbers sometimes fail or are blocked out of the plastic under adverse weather conditions before the lifetime of the protected material. Also, it is not possible to use all of these ultraviolet absorbers with radiation curing of the plastic material. Another disadvantage of these ultraviolet absorbers is the high amount of absorber needed for protection of some materials.
Hydroxy,alkoxybenzophenone compounds are known to be effective ultraviolet light absorbers and stabilizers. For example, in U.S. Pat. No. 4,186,151, there is disclosed in detail literature and patent references relating to such compounds and derivatives thereof. Additionally, in U.S. Pat. No. 4,177,122 there is described the preparation of ultraviolet light sensitive compounds obtained by reacting a hydroxybenzophenone with an alkylene oxide and esterifying with an unsaturated end group, which are useful particularly in making printing inks.